Experimental Plots at Rolhamsted, from 1864 to 1883. 435 
of nitrogen have been carried off, thus leaving 60 lbs. of 
nitrogen to be accounted for ! 
In the autumn of 1881, the soil in the various experimental 
plots was sampled and analysed, both for the total nitrogen and 
lor nitric acid, to the depth of 27 inches. Although the soil 
of plots 17 and 18 contained rather more total nitrogen and 
nitrates than plot 5, still — within the range examined — there 
was no evidence of the existence in the soil of the large amount 
of nitrogen supplied in the manure, and not accounted for in 
the crop. 
It is quite certain, therefore, that when salts of ammonia 
are applied to grow wheat, it is not safe to calculate upon any 
of the unexhausted residue being available for the purpose of 
growing a second corn-crop. 
There is also evidence to show that the exhausting character 
which practical farmers attribute to corn crops, is quite as much 
due to the nitrogen which they do not assimilate being washed 
out of the soil, as it is to the amount of that substance which is 
removed in the produce. 
Mixed Minerals with Salts of Ammonia and Nitrate of Soda, 
Having already given the result of experiments on which 
mixed minerals were used alone, as also where salts of ammonia 
were used alone, we now come to another series of experiments, 
where one uniform quantity of mixed minerals was used in each 
case, but with different amounts of nitrogen in the form of salts 
of ammonia, and also as nitrate of soda. The applications were 
as follows : — Plot 6 A and B received 200 lbs. of sulphate and 
muriate of ammonia, containing 43 lbs. of nitrogen ; plot 7 A 
and B, 400 lbs. of the same salts, containing 86 lbs. of nitrogen ; 
and plot 8 A and B, 600 lbs. of the same salts, containing 
129 lbs. of nitrogen ; while plot 9 A, received 86 lbs. of 
nitrogen as nitrate of soda, instead of salts of ammonia. 
For the first twelve years of the experiment, we further em- 
ployed on plot 16 a and B, 800 lbs. of salts of ammonia, con- 
taining 172 lbs. of nitrogen ; but even in 1863 — a season which 
for productiveness is not likely to be repeated except at rare 
intervals — the 800 lbs. produced so small an increase over the 
manure containing 600 lbs. of ammonia, that it was decided to 
stop the application, with the view of obtaining, by this means, * 
some information in regard to the unexhausted residue of 
manures. 
In the following table is given — in 4 periods of 8 years each — 
the produce of wheat grown by the minerals and nitrogen in 
various proportions for 32 years in succession ; and for com- 
